1. Field of the Invention
The present invention is related to a buck-boost switching converter, and particularly to a highly efficient control circuit and method for a buck-boost switching converter.
2. Brief Description of the Related Art
In order to maintain an electronic device installed with batteries to provide a steady input power source, usually the buck-boost converter is utilized to regulate the power source. However, the conventional buck-boost converter is less effective and it is essential to promote the efficiency thereof to meet the tendency for requiring a modernized electronic device.
U.S. Pat. No. 6,166,527 entitled “CONTROL CIRCUIT AND METHOD FOR MAINTAINING HIGH EFFICIENCY IN A BUCK-BOOST SWITCHING REGULATOR” proposes that the switching regulator can be operated in a buck mode in case of the input voltage being higher, in a buck-boost mode in case of the input voltage approaching the standard output voltage, and in a boost mode in case of the input voltage being lower for keeping the converter with high efficiency in operation. However, the buck-boost switching regulator of the prior reference still has deficiencies which are worth to improve substantially.